Three-dimensional haptic manipulator controlled game in the treatment of developmental coordination disorder

Transcription

1 Three-dimensional haptic manipulator controlled game in the treatment of developmental coordination disorder Anna Wałach and Agnieszka Szczęsna Abstract Computer games are more and more used for serious purposes not only for entertainment. In few last years we can observe very fast market development of serious games. They are used to education, simulation, research, health and therapy purposes. This article describes a game controlled by Phantom Omni device that could be a rehabilitation tool in the treatment of developmental coordination disorder. The game focuses on usage of the feedback generated by the haptic device. Key words: serious game, developmental coordination disorder, haptic manipulator 1 Introduction Specialized devices are being developed to resemble real-world reaction and be able to precisely identify operator s movements and intentions. The kind that focuses on generating real-time responses is called haptic devices. The most important feature of this type of controller is a tactile feedback produced by it that render the feeling of the texture and shape of objects shown on the screen of the computer. Haptic devices are widely used in medicine. Haptic devices using virtual reality have been suggested to enhance the stroke rehabilitation. Research Agnieszka Szczęsna Silesian University of Technology, Institute of Informatics, ul. Akademicka 16, Gliwice, Poland, agnieszka.szczesna@polsl.pl Anna Wałach Silesian University of Technology, Institute of Informatics, ul. Akademicka 16, Gliwice, Poland 1

2 2 Anna Wałach and Agnieszka Szczęsna implies that haptic-based virtual rehabilitation offers a potential tool in motor and cognitive rehabilitation, with a wide range of applicability [1], [2]. Studies show increasing number of neurodevelopmental disorders being diagnosed among children and adults. One of them is dyspraxia, also known as developmental coordination disorder (DCD), an inability to plan, organize and coordinate movement [3]. Depending on the level of severity, it can be a reason of small difficulties in everyday activities, for example fastening buttons or shoelaces, but may also make one unable to drive a car because of affecting working memory and coordination skills. There are several various difficulties that occur during treatment of DCD. One of the most significant obstacles is a problem with conducting proper diagnose. Another - existing systems of therapy, not all of them equally effective, but all requiring experts in rehabilitation or psychology and hours of exercises with professionals. DCD is very often observed among children in the primary school. The most efficient way of engagement into the exercise this age group seems to be the serious game. It allows to develop the necessary coordination or mental skills. Disguising the exercise as a game makes it more entertaining and pleasurable for a child. Serious game is a general term used for application that is developed using a computer game technology and game design principles but are used for nonentertainment purposes [4]. We can say that these applications are any sort of interactive computer-based game software for one or multiple players to be used on any platform and that has been developed with the intention to be more than entertainment [5]. The idea is such games could be used for more serious purposes such as education, simulating real world phenomenon and relations, increasing life quality through health, rehabilitation and therapy applications or raising interest to the problems in our global world [6]. The main point of serious games is: to get players to learn something and, if possible, have fun doing it. Enjoyment increases the player s engagement. One of main group of serious games are games for health [7], [8], [9], [10]. Games are rapidly becoming an important tool for improving health behaviors ranging from healthy lifestyle habits and behavior modification, to self-management of illness and chronic conditions to motivating and supporting physical activity. The findings also suggest that play and entertainment can be effective foundations for serious interventions in health care. This article describes a coordination improving serious game, controlled by 3-dimensional haptic device that could be an effective tool in rehabilitation of children with dyspraxia.

3 Three-dimensional haptic manipulator controlled game in DCD 3 2 Developmental Dyspraxia Developmental Coordination Disorder (DCD), also known as developmental dyspraxia, is the inability to plan, organize and coordinate movement [3], [11], [12], [13], [14]. It results in fine and gross motor problems and/or speech difficulties, which can have strong negative impact on daily activities and school achievements. Dyspraxia was first described by WHO in It is a hard to diagnose and even harder to cure motor disorder, which is subcategory of neurodevelopmental disorder along with autism and Down syndrome - and mostly identified among children. It often appears together with neurological illnesses from other subcategories, like ADHD, Asperger syndrome or dyslexia [15]. It is, however, also sporadically detected in completely healthy (except for DCD) children who are developing well intellectually. DCD is not caused by motor or sensory impairments, similar to muscular dystrophy or Parkinson s disease. No correlation to any known neurological condition or intellectual impairment could be found. 2.1 Treatment The treatment for DCD is based on rehabilitation and training. No pharmacological therapy was designed to be used during DCD s treatment. Medications are reserved for the treatment of associated conditions (e.g., attention deficit hyperactivity disorder, ADHD) [16]. There are two basic approaches of rehabilitation procedure: top-down and bottom-up. The top-down approach, also known as task-oriented or modular, attempts to remedy or improve specific difficulties by employing specific techniques aimed at the observed motor challenge (e.q. difficulty with handwriting, catching a ball, or performing fine motor tasks with the fingers). It usually involves gradually targeting certain problem behaviours and implementing step-by-step interventions that focus on teaching and practicing the skill [16]. The most important element of modular-approach is practice. Practical applications of this method are therapies such as the cognitive motor approach with task orientation or task-oriented approaches with motor learning. The bottom-up approach (process-oriented, deficit-oriented), the more global or generalized one is based on the theoretical assumption that the motor skills problem is just a manifestation of some underlying mechanism, such as impaired sensory integration or insufficient or inaccurate kinesthetic perceptions. In the bottom-up approach, the therapist does not initially address the observable motor challenge. Rather, the expert focuses on how children manage their bodies, process stimulation (sensory information), and deal with problems. The expectation is that the improved sensory-motor (sensorimotor) functioning becomes generalized and eventually improves the motor

4 4 Anna Wałach and Agnieszka Szczęsna skills. As children become comfortable with their bodies, they gain control of their motor (and other) functions [16]. This method is represented by the kinesthetic training approach, sensorimotor integration therapy and sensory integration therapy. No researches show that any of this approaches is definitely effective as DCD s treatment. This is probably caused by great diversity in symptoms and severity s levels of DCD. However, data suggest that top-down approach may be more efficient than bottom-up. 3 Haptic devices in rehabilitation In this particular area there has been great interest in research how computer haptics technology can assist in rehabilitation process of people who has had some damage to their motor skills, while playing a game. The combination of the properties inherent to computer haptics (force and tactile feedback) with the appealing and motivating factor offered by games with virtual reality have provided a framework for the development of various rehabilitation systems that often involve the patient, and the therapists [17]. There are researches that prove the sensorimotor control of limb stiffness and compliance is a key element in the organization of movement. Though, the best training approach would be the sensorimotor training. The goal of this therapy is to improve child s perceptual abilities intrinsic to the concurrent generation and experience of their own movements as well as use of this information to guide their movements [18]. This kind of training is difficult to apply with traditional therapeutic tools. However, various robot-assisted therapies are developed in order to support sensorimotor training, some of them including haptic devices. Robot-assisted therapies allowed to perform rehabilitation without the direct supervision of a trained therapist, what is especially important in DCD, where the number of patients significantly outgrows number of therapists. What s more, the complexity or/and difficulty of the task can be controlled very precisely. Haptic devices were used to improve the generation of handwriting movements of children with DCD [19]. The researches show that this method can be notably effective, mostly because of active sensorimotor generation and control of movement trajectories. This is the feature required for learning generalized to task-related movements other than those specifically practiced [18]. This requirement is caused by catch-22 situation connected with movement learning mechanism. This learning process for a person without dyspraxia consists of two stages. First one is learning to generate imprecise approximation of movement. When this is achieved, one can gradually improve approximation of a movement through practice until achieving optimal route. For people with dyspraxia it is almost impossible to generate good enough

5 Three-dimensional haptic manipulator controlled game in DCD 5 qualitative approximation, which should allow them to make quantitative improvements through practice - this is a catch-22. It is possible to overcome this paradox only if the support from the machine is balanced with possibility of active generation and control of movement from child. Mechanical properties of haptic devices, like inertia and tactile feedback can significantly help in achieving this result [18]. Using haptic devices as controllers in application allows to benefit from the various factors generated by particular devices. These factors vary between products. The Phantom Omni device consists of stylus connected to an arm mounted on base. It has 6 degrees of freedom and its workspace range is 160x120x70mm. Thanks to its pen-like stylus it is easy and natural to operate it, especially for children. Phantom Omni has been widely used in industry for a several years, also for medical purposes, thus it is well tested and safe-in-use device. The haptic factors generated by this device and tested in children s rehabilitation are [19] [18]: inertia, viscosity (of the space), magnetic attraction (of the object), friction (of the object). Viscosity and inertia may provide an appropriate support, but do not allow to keep track of designed movement form. Furthermore, no evidence suggest that the method could generalize the performance without support from the device [19]. Magnetic attraction help in following the generated path and this is the main haptic factor that will be used in the project. Researches show that friction has no significant impact on helping the child in performing the task [18]. 4 Game rules analysis The main task performed by patients is to follow the three-dimensional wire with tip of stylus, where the path is magnetically attractive. There is an object that player has to move from start to end along the path by pushing it with the tip of stylus, represented by cursor. There is also a competitor s object, moving along the path with uniform velocity (specified for each curve). The player wins a round when his object reaches the end before competitor s one. In order to develop a serious game which can help children with dyspraxia, some basic rules and presumption must be established. The following principles are based on [18]: 1. The game represents a bottom-up approach with sensorimotor training. 2. Basic task is to follow the path with tip of stylus, where the path is magnetically attractive. 3. The main haptic factor is magnetic attraction. 4. There must exists a levelling system.

6 6 Anna Wałach and Agnieszka Szczęsna 5 Implementation The game is implemented in C++ with OpenGL and Haptic Library API (under Academic License) to support Phantom Omni haptic device. 5.1 Path The mathematical representation of path is the Bezier curve (Fig. 2). Depending on level of difficulty there are different curves - they vary in length, curvature and torsion. There are three designed curves. Each curve has defined two times of passing - one for slower and one for faster race. The competitor s speed is calculated based on this time and the current path length. Depending on the level of difficulty, curves have 7, 10 or 12 control points. The curve representation in the game is built from many single spheres, coordinates of canter are calculated in the following way: ) where (x,y,z) = ( n i=0 x i B n i (t), n i=0 y i B n i (t), n i=0 z i B n i (t) for t [0,1] (1) {( n ) B n i (t) = i t i (1 t) n i for i = 0...n 0 for i < 0, i > n (2) and n 1 - number of control points. The step of t incrementation is 1/500 = 0.002, because 500 spheres are generated for each curve. 5.2 Levelling up There are three parameters that are changing along the game: the competitor s velocity, the path s shape (and length), the magnetic attraction level. The player advances to the next level when he wins two times in a row with definite settings. While advancing, firstly, the competitor s velocity is increased. Then, when the player wins with both competitors, slow and fast one, he change the path to more advance, but with slower competitor again. Finally, after winning games on all paths, the magnetic attraction level is decreased and player starts from the very first path with slower competitor. This process is repeated until reaching the lowest possible level of magnetic attraction and is presented in Fig. 1.

7 Three-dimensional haptic manipulator controlled game in DCD 7 Fig. 1 Schema of levelling process 5.3 Measuring player s score Continuous measuring player s score during a game is one of the most important parts of the project, as it allows to control his progress. There are two main values measured during the game: path length (of the object controlled by the player) and total race time. The path length may differ from curve length in case player leaves the magnetic field of a wire. This affect more often children with dyspraxia. This parameter decreases while trainings and therefore is index of progress. Total race time is a parameter responsible for determining of win. The counting starts from the moment when player s object moves for a first time in a round and lasts until reaching the end point. 5.4 Progress detecting Progress detecting is a process that repeat with 50 Hz frequency. It has to determine if the player is able to move his object or not by detecting the collision of path and cursor.

8 8 Anna Wałach and Agnieszka Szczęsna The information, that player is touching the path, comes from haptic thread. It has appropriate properties set if such event is happening. The problem is in checking on which part of path player is now. The whole path cannot be checked during the short time (not even 20 ms) because it would require checking collision with even 500 elements that path consists of. The approximation is used, that in current moment of time application tests only 10 elements (points) that lie on the path just in front of the player s object - if the cursor collide with any of these points, object is moving to this point and procedure is repeated until end of path. The collision is calculated from sphere equation: (x x 0 ) 2 + (y y 0 ) 2 + (z z 0 ) 2 <= r 2 (3) where x 0,y 0,z 0 - current path element centre coordinates; x,y,z - player coordinates; r - empirically determined radius with value Route calculation Player actual position and visualised position differ. Path magnetically attracts the cursor, so as a result there is a specified radius (different for each difficulty level) in which player can move without having his cursor unhook from the path. If player moves out of the range of the magnetic field, the cursor will move as well. Therefore, the route is measured based on the real movements, not just the ones displayed to player. The route is calculated using the following expression: L = n 1 (x i x i+1 ) 2 + (y i y i+1 ) 2 + (z i z i+1 ) 2 (4) i=1 where n - number of all points collected during measuring the route; x,y,z - point coordinates. 6 Game In the Fig. 2 first path from game is presented. In Fig. 3 the player s object real route is showed. The sharp impulses are effects of sudden getting out of the range of magnetic attraction field (it requires pressure which is hard to control when the field disappears). The game is ready to be presented to a children with dyspraxia as a rehabilitation tool. Although adding some more children-friendly features (like sounds, more colourful and friendly objects) may be considered to allows

9 Three-dimensional haptic manipulator controlled game in DCD 9 Fig. 2 First curve, the lowest level. Fig. 3 The route of the player s object. better interaction with patients, it is not required for application to work properly. 7 Summary The project was successful. All requirements have been implemented. Fully functional, stand-alone application has been created. The next stage of the project should be evaluation with children, so the game fulfils their requirements and then perform tests, in which application would be used as a rehabilitation tool for children with dyspraxia. The Development Coordination Disorder is a troublesome disease, also because of psychological and social reasons. Engaging in the development of treatment for this disorder was a really valuable experience. Acknowledgements This work was performed using the infrastructure supported by POIG /13 grant: GCONiI - Upper-Silesian Center for Scientific Computation.

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